This invention relates to magnetic tape cassettes. In particular, it relates to a small video cassette having a slide type brake member which is adapted to stop the rotation of the tape reels in the cassette.
The structure of a conventional brake member of this type is as shown in FIGS. 1, 2, and 3. FIG. 1 is a perspective view of the brake member. FIG. 2 is a sectional view showing a state of the brake member when the cassette is stored (or not in use), and FIG. 3 is a sectional view showing another state of the brake member when the cassette is in use.
The brake member 1 has an internal hole 1b receiving an actuating pin to move the member. A pair of arms 1a engage gears on the reels to prevent motion. The arms 1a have notched recesses 1c to reduce sliding friction by reducing the sliding contact surface area between the brake member and the cassette.
As shown in FIG. 2, a brake member 1 (FIG. 1) is arranged in alignment with a brake releasing bar insertion hole 2a in the lower half 2 of the cassette. The brake member 1 is biased towards reels 5, so that each end part 1a of the brake member 1 locks the gear 5a of a respective reel 5. Since the end portions are angularly spread effective locking of both reels occurs. The brake member 1 is depressed against the lower half 2 by an elastic member 4. The prior art magnetic tape cassette is constructed as described above.
When the cassette is not in use, the reels 5 are not turned and accordingly, the tape is not slackened or unwound. When the cassette is used, a brake releasing bar 6 having a tapered insertion end is inserted into the brake member from the video deck as shown in FIG. 3. The tapered end portion bears against the lower wall of brake member to slide it away from the reels 5. As the member 1 moves to the left, the reels are unlocked.
The brake member 1 has a hole 1b and recesses 1c as illustrated in FIGS. 1 through 3. Therefore, not only when the cassette is used, but also when it is not used (or it is stored) dust or the like may enter into the cassette as indicated by the arrows in FIG. 3. If dust or the like enters the cassette, the picture recording and reproducing characteristics of the tape is ultimately lowered, for instance, because of signal drop-out. In a small video cassette, the possibility that dust or the like enters the cassette is further increased because these units are widely used in conjunction with portable systems.